Green tea consumption improves plasma lipid profiles in adults

Nutrition Research 26 (2006) 604 – 607 www.elsevier.com/locate/nutres

Communication

Green tea consumption improves plasma lipid profiles in adults Susana Coimbraa,4, Alice Santos-Silvaa,b, Petronila Rocha-Pereirab,c, Susana Rochaa,b, Elisabeth Castroa,b a

Faculdade de Farma´cia, Servic¸o de Bioquı´mica, Universidade de Porto, 4057-040 Porto, Portugal b Instituto de Biologia Molecular e Celular, Universidade Porto, 4150-180 Porto, Portugal c Departamento de Quı´mica, Universidade Beira Interior, 6201-001 Covilha˜, Portugal Received 26 June 2006; revised 31 August 2006; accepted 15 September 2006

Abstract Cardiovascular disease is the major cause of mortality and morbidity in the Western world. Green tea prepared with leaves of Camellia sinensis is particularly rich in antioxidants, which seem to have a crucial role in atherogenesis. The aim of our investigation was to evaluate the effect of green tea drinking on the lipid profile in 29 Portuguese subjects. The lipid profile included the measurement of total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, triacylglycerols, apolipoprotein A-I, apolipoprotein B, and lipoprotein(a). The measurements were performed at the beginning of the study, and after 3 weeks of drinking 1 L of water, and after 4 weeks of drinking 1 L of green tea daily. Tea was prepared every day at the same conditions of temperature, time of infusion, and concentration. No dilution effect was observed after water drinking. After drinking green tea, a significant beneficial improvement in the lipid profile of subjects was observed. A decrease in cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, and ratio of cholesterol/HDL-C, but an increase in HDL-C and apolipoprotein A-I, was observed in the subjects. No significant differences were observed for triacylglycerol and lipoprotein(a). Our data suggest that drinking green tea has a beneficial effect protecting against the risk for cardiovascular disease by improving blood lipid levels. D 2006 Elsevier Inc. All rights reserved. Keywords:

Green tea; Risk factors; Lipid profile; Camellia sinensis; Cardiovascular diseases

1. Introduction Tea is an infusion prepared with the leaves of Camellia sinensis. Excluding water, tea is the most widely consumed beverage in the world. A different processing of the leaves defines the characteristic of the obtained tea: green, oolong, and black [1]. Green tea is an important source of flavonoids, namely, catechins, which are strong antioxidants. Cardiovascular pathologies are one of the major causes of mortality and morbidity in the western world [2]. The search for factors that could decrease the prevalence of

4 Corresponding author. Tel.: +351 962677495; fax: +351 222086027. E-mail address: [email protected] (S. Coimbra). 0271-5317/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.nutres.2006.09.014

cardiovascular disease (CVD) continues as an active area of research. Several epidemiologic and clinical studies [3-12] have shown that high levels of total cholesterol, triacylglycerols (TGs), low-density lipoprotein cholesterol (LDL-C), apolipoprotein A-I (Apo A-I), and lipoprotein(a) [Lp(a)], and low levels of high-density lipoprotein cholesterol (HDL-C) and apolipoprotein B (Apo B), are risk factors for CVD, among several others. According to the oxidative modification hypothesis for atherogenesis, reactive oxygen species may contribute to the events leading to the inception and progression of atherogenic lesions by promoting oxidation of LDL. The most striking changes in atherogenic lesions include accumulation of lipids followed by infiltration, activation,

S. Coimbra et al. / Nutrition Research 26 (2006) 604–607

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Table 1 Effect of water and green tea drinking in lipid profile (mean F SD) n = 29 Cholesterol (mg/dL) HDL-C (mg/dL) LDL-C (mg/dL) TG (mg/dL) Apo A-I (mg/dL) Apo B (mg/dL) CT/HDL-C

BL 210.3 56.4 136.2 101.8 150.8 92.9 3.9

F F F F F F F

36.8 10.6 34.6 56.6 38.4 21.1 1.0

W 215.7 57.7 140.3 102.1 149.5 92.7 3.9

F F F F F F F

39.1 13.0 37.5 45.8 35.9 22.7 1.0

P (BL vs W) NS NS NS NS NS NS NS

GT 209.1 60.3 127.4 106.0 156.8 89.0 3.7

F F F F F F F

36.6 15.7 33.7 53.0 39.6 20.6 1.1

%D 2.8 +4.0 8.9 +4.8 +5.1 3.6 6.0

P (BL vs GT) b .05 b .01 b .001 NS b .05 b .01 b .001

BL indicates basal level; W, water; GT, green tea; NS, not significant; CT, cholesterol.

and overgrowth of cells. In the subendothelial space, LDL is oxidatively modified by reactive oxygen species produced by activated inflammatory cells, becoming a chemotactic factor for circulating monocytes, inhibiting the motility of the resident macrophages, and being much more avidly phagocytosed by macrophages than the native LDL. The potential antioxidant bioactivity of green tea may, therefore, have a crucial role in reducing the risk of atherogenesis. Several studies suggest that green and black tea drinking may offer a protection for CVD. The protection seems to increase with the volume of tea consumed daily [13]. An increase in daily tea drinking of 711 mL was reported to reduce the risk of myocardial infarction by 11% [14]. Endothelium-dependent vasodilatation, which is known to be impaired in heart disease patients and in subjects with high cholesterol levels, was reported to improve significantly after drinking tea daily for 4 weeks [15,16]. Green tea drinking has also been associated with lower serum levels of cholesterol, TG, and LDL-C, but higher serum levels of HDL-C [17-21]. Most of the reported studies that examined the effect of green tea drinking in lipid risk factors for CVD have been performed in animals. Considering the importance of tea drinking in human dietary habits worldwide and the high prevalence of CVD, researchers warranted further studies about the actions of tea. Therefore, the aim of the present study was to evaluate the effect of green tea drinking on lipid risk factors associated with CVDs. 2. Methods and materials 2.1. Study design Twenty-nine healthy subjects (7 men and 22 women), 22 to 63 years old, with a body mass index of 25.0 F 4.8 kg/m2, volunteered and gave their written and informed consent to participate in this study. The protocol and human use was approved by the Ethic Committee of Instituto de Biologia Molecular e Celular, Universidade Porto, Portugal. None of the subjects consumed more than 2 cups of red wine per day; 21 of the studied subjects were nonsmokers. None of the studied individuals presented known clinical, biochemical, or hematological manifestations of cardiovascular, hepatic, renal, or endocrine disorders. The subjects were not under any lipid-lowering medication or under any diet supplementation. The analytic evaluations were per-

formed at the beginning of the study, after 3 weeks of drinking 1 L of water daily, and after 1 L of green tea daily for 4 weeks. Green tea was prepared everyday at the same temperature (70-808C), time of infusion (2.5 minutes), and concentration (1.75 g of tea leaves for 200 mL of water). These conditions aimed to prepare a tea with a rich and adequate concentration, but also to obtain a pleasure beverage [22,23]. The subjects were asked to drink the water during the water period and the tea during the green tea period during the day, and asked to maintain their food and drinking habits at mealtime. No milk was added to the tea preparations. 2.2. Collection and preparation of blood samples Venous blood samples were collected at rest and fasted for 12 hours. After centrifugation, serum aliquots were prepared and stored at 808C until assayed. 2.3. Lipid analyses The lipid measurements included cholesterol, TG, HDLC, LDL-C, Apo A-I, Apo B, and Lp(a). Cholesterol and TG were measured by enzymatic-colorimetric assays using commercially available kits (Randox Laboratories, Antrim, UK); HDL-C and LDL-C were performed by using direct methods (Randox Laboratories); Apo A-I, Apo B, and Lp(a) were determined by immunoturbidimetric assays (Randox Laboratories). 2.4. Statistical analysis Results are expressed as mean F SD and as median values (inter quartile ranges). For statistical analysis, the Statistical Package for Social Sciences, version 2.0 was used (SPSS, Chicago, Ill). To determine the differences occurring for each subject during the study, we used a paired Student t test whenever the parameters presented a Gaussian distribution and Mann-Whitney test in the case of a non-Gaussian distribution, as occurred for Lp(a) values. A P value lower than .05 was considered as statistically significant. 3. Results and discussion No dilution effect was observed (Table 1) as shown by the evaluation of the lipid profile before and after 3 weeks of drinking 1 L of water daily (basal levels vs water drinking

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period). When comparing the lipid profile presented after the water drinking period, with those presented after green tea drinking, we found a significant reduction in cholesterol, LDL-C, and Apo B, and a significant increase in HDL-C and in Apo A-I; no significant differences were observed for TG (Table 1). No significant differences were found between the median values for Lp(a) observed after the water (25.5 [16.5-84.3]) and green tea (22.6 [17.0-87.1], P N .05) treatments. Analyzing each parameter included in the lipid profile, for each study subject, we did not observe a beneficial effect after green tea drinking in 9 individuals of 29 for cholesterol, HDL-C, Apo A-I, and Apo B. In the case of LDL-C, only 3 subjects did not show a beneficial effect after green tea drinking. It is important to note that the individuals who did not show a beneficial effect were not the same for each of the lipids measured. In the case of TG, which did not present a statistically significant change after green tea drinking, we found, however, that 13 of 29 individuals presented a beneficial effect. In the past few years, tea prepared from the leaves from C. sinensis, namely, green and black teas, has been largely studied by the scientific community. Tea appears to provide an important source of antioxidants, which seem to play a crucial role in several pathologies associated with oxidative stress, such as CVD [24]. However, most of the studies about the effect of green tea drinking on lipid risk factors for CVD have been performed in animals. Considering the importance of tea drinking in the human diet and the high prevalence of CVD, further studies about that effect are needed. In the present study, we found that green tea drinking imposed significant beneficial changes in the lipid profile of subjects. We observed a significant hypocholesterolemic effect for green tea, which is in accordance with other reports in human [17,20] and animal studies [19,25-29]. This effect is attributed to a reduction in cholesterol absorption and to an increased excretion of biliary acids and cholesterol; another proposed action is the inhibition of cholesterol synthesis in the liver [28]. We did not find a significant improvement in TG after green tea drinking, although some authors have reported significant reductions [25,29]. It is possible that a longer period of green tea drinking could impose the expected improvement; however, the physiologic differences usually observed in TG may account for our results. A significant reduction was observed for LDL-C and, as expected, for Apo B, because this is the most abundant apolipoprotein in LDL. A significant increase was observed in HDL-C, as well as in its most important apolipoprotein, Apo A-I. These changes in LDL-C and in HDL-C are in accordance with several studies [19,20,25,29]. In contrast, Lp(a), an independent risk factor for CVD [3,8], showed no significant difference after green tea drinking. The protective effect of green tea for CVD has been attributed to its high content of flavonoids [13,14,30,31],

particularly in catechins, which are strong antioxidants. The antioxidants provided by green tea drinking may account for the inhibition in lipid peroxidation chain reactions [32] that scavenge nitric and oxygen radical species [33,34]. A recent study in our laboratory [35], using the same experimental protocol, showed that green tea drinking induced a significant reduction in serum levels of MDA (malonydialdehyde) and MDA+4-HNE (malonydialdehyde + 4-hidroxy-2-nonenal) and in oxidative stress within erythrocytes; a rise in the antioxidant capacity was also observed. These data suggest a beneficial action for green tea drinking that could reduce the development of or the enhancement in oxidative stress and, therefore, protect the individual against oxidative stress. Green tea is particularly rich in epigallocatechin, a powerful antioxidant [34,36]. Some in vitro studies showed indicate that epigallocathechin exerts a protective effect against lipoprotein oxidation, namely, against LDL oxidation. It is known that the oxidatively modified LDL has a central role in atherogenesis. When analyzing individually the results obtained for each of the parameters included in the lipid profile, we found that more striking improvement with green tea drinking was observed for LDL-C. A reduction in LDL-C was observed in 90% of the studied individuals. For cholesterol, HDL-C, and Apo A-I, an improvement was observed in 69% of the individuals. These results suggest a particularly important effect of green tea drinking upon LDL-C levels. The effect of green tea drinking in lipid profiles have been widely studied in animals [25-29] and in humans [17,20,37-40]; however, controversial results are reported, although the animal studies offer more consistent data. This controversy may be related to differences in the study design, namely, in dietary and lifestyle habits, and/or in the experimental protocols. Of the many reported methods for the preparation of tea, temperature, time of infusion, and concentration are important. In addition, the time of green tea consumption may also contribute to the controversy. Our data suggest that green tea drinking has beneficial effects, which protects against CVD by improving blood lipid profiles. Further studies that would examine additional parameters of green tea consumption in humans are needed. It would be important to further clarify the effect of regular green tea consumption and the way it should be prepared to achieve a healthy effect. References [1] Beecher GR, Warden BA, Merken H. Analysis of tea polyphenols. Proc Soc Exp Biol Med 1999;220(4):267 - 70. [2] Ferrie` res J. E´ pidemiologie et athe´ roscle´ rose. Sang Thrombose Vaisseaux 1998;10(6):339 - 42. [3] Schwartzman RA, Cox ID, Poloniecki J. Elevated plasma lipoprotein (a) is associated with coronary artery disease in patients with chronic stable angina pectoris. J Am Coll Cardiol 1998;31(6):1260 - 6. [4] Horejsi B, Ceska R. Apolipoproteins and atherosclerosis: apolipoprotein E and apolipoprotein (a) as candidate genes of premature development of atherosclerosis. Physiol Res 2000;49(S1):S63 - 9.

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